<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app">
        <h1>{{ enter }}</h1>
        <input type="text" v-model.trim="enter"> 
    </div>
    <script src="https://unpkg.com/vue@3/dist/vue.global.js"></script>
    <script>
        new Vue({
            el: "#app",
            data: {
                msg: "Hello world",
                enter: ""
            }
        })
    </script>
</body>
</html>